Coil-On-Plug technology

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Ignition Systems & New Technology

Since vehicles with direct ignition systems were first introduced in 1988, an ever-increasing number of new cars and trucks are being manufactured using Coil-On-Plug (COP) technology for ignition systems. In fact, the majority of new vehicles being produced today utilize a direct ignition system. With this new technology replacing the traditional ignition system where ignition wires are present, it is beneficial to understand a direct ignition system before you run to your local AutoZone store. This knowledge will help ensure that you purchase the correct components, saving you time and money.

Coil-On-Plug (COP) Ignition Systems

Coil-On-Plug (COP) is a type of distributor-less ignition system in which individual ignition coils are mounted directly over each spark plug and no spark plug wires are required. Unlike traditional ignition systems that use a single high-voltage coil to route voltage to each of the spark plugs through a distributor, COP systems use individual coils that are controlled electronically by a combination of the car’s computer and a crankshaft or camshaft position sensor.

The Coil-On Plug system is usually comprised of three parts:

1. The electronic coil
2. The spring or terminal-type connection used to connect the coil to the spark plug, and
3. The insulator that covers the connection (see figure below).

Designs using a replaceable insulator (see Figure A) allow the insulator and spring to easily separate from the coil for quick replacement during a tune-up. In a non-replaceable design, the insulator and spring are permanently mated to the coil and the entire assembly needs to be replaced (see Figure B).

"Slave" Systems

Waste Spark Distribution systems, or "Slave" systems, are another type of COP ignition system (see figure C). They are comprised of a single coil per two cylinders; i.e., a V6 engine would have three coils. The coils are mounted to the spark plugs on one half of the engine cylinders, and a typical ignition wire connects these coils to the "slave" cylinders (those cylinders on the opposing end of the 4-stroke engine cycle).

Changing Your COP Insulators

If you can change the spark plugs on your vehicle then you can certainly change the coil-on-plug insulators as well. Adding this step to your tune-up is quick, easy and inexpensive.

• As noted earlier, the COP insulator sits directly on top of the spark plug and is typically bolted to the valve cover.
• You’ll need a socket wrench to remove them (it’s always a good idea to clean the area around the coil prior to removing them to ensure that no dirt or grime falls into the open spark plug well).
• With the coil now removed from the valve cover, you can either leave the coil connected to the harness to replace the insulator or disconnect the coil from the harness, replacing the insulator on a bench top.
• Before removing the insulator, examine both the old insulator and the new insulator, noting any mating features that may be present.
• Grasp the top of the coil in one hand and grasp the insulator in the other hand with your thumb and forefinger positioned where the insulator meets the coil. With a slight twisting motion slowly and carefully pry the insulator off of the coil.
  • SPECIAL NOTE: It is recommended you remove the insulator over a clean, flat working surface. Some coils may contain very small resistors that can be easily lost or dropped into the spark plug well. Some applications use replaceable spring contacts to connect the coil to the spark plug while others are integrated into the coil or insulator.
• If there is a separate spring contact included with your new insulator, carefully remove the old spring contact from the coil. With the old insulator and spring removed, carefully clean the coil.
• Apply a thin coating of dielectric grease to the inside of the insulator on both the coil and spark plug end.
• Install the new spring contact and then install the new insulator onto the coil, making sure to orient the insulator into the same position as the original.
• Reconnect the coil to the harness (if you disconnected it), place the coil back into position over the spark plug and bolt the coil back to the valve cover.

Maintaining Your COP Ignition System

Changing your COP insulators each time the spark plugs are replaced (about every 50,000 miles but may vary by vehicle) is an excellent way to ensure peak engine performance and reduce potential ignition problems. Despite their durability, re-installing "old" insulators may result in dielectric failure and is not recommended. COP insulators will degrade after prolonged exposure to heat and operating voltage, which can lead to dielectric leaks, causing engine misfiring, fouled spark plugs or a rough-running engine. Replacing the insulators eliminates the need to replace a complete coil assembly, which is costly and most times unnecessary, as coils typically do not fail but insulators are often damaged when removed from the direct ignition system.

Conclusion

Replacing COP insulators is a cost-effective solution for insulators that fail due to normal wear and tear or may be damaged during tune-ups. Like changing your ignition wires during a routine tune-up, changing your COP insulators should be included as part of a normal tune-up, ensuring that both your vehicle and its engine last longer and perform better.